1. Field of the Invention
The present invention is related to a motorized hand tool for turning screw bolts and nuts. According to the present invention, a motorized screw bolt driving tool for turning screw bolts and nuts generally includes a housing having received therein a motor, a centrifugal element comprising a pair of fins with a spring connected therebetween; a spindle comprising an axle having an arch-shaped projection at its rear end defining therewith two retaining edges; a brake socket having a pair of unitary pins respectively inserted into a swivel element; a swivel element having a notch for positioning therein of a brake element and two pin holes for insertion therein of the two pins of the brake socket; a spindle holder received in the swivel element to hold the spindle. When the motor is turned on, the centrifugal element drives the brake socket to disengage from the swivel element permitting the brake element to swing in the notch of the swivel element so that the spindle can be driven to rotate clockwise of counterclockwise for further operation in turning a screw bolt or nut.
2. Description of the Prior Art
In turning screw bolts or nuts a hand-operated or pneumatic power operated tool may required to facilitate the operation. There is a variety of hand-operated tools for turning screw bolts and nuts according to specific requirement, such as spanner, monkey wrench, screw wrench etc. Regular pneumatic power operated tools for turning screw bolts and nuts generally utilize pneumatic power to drive a spindle to rotate so as to further carry a socket to turn a screw bolt or nut. In comparison with pneumatic power operated tools, hand-operated tools are more easy to operate and convenient to carry. However, in some conditions, hand-operated tools may be useless. For instance, if a bolt is rusted or tightly screwed up with a thing, it is difficult to screw loose such a bolt with a regular hand-operated tool, and a pneumatic power operated tool may be required under this case. However, conventional pneumatic power operated tools are very expensive, heavy, not convenient for carriage, and they may make much noise during during operation. Because of the said problems, pneumatic power operated tools can not be widely accepted by consumers for regular use. In recently, a kind of directly motorized and light-weighted screw bolt driving tool has been specially designed for use to turn screw bolts and nuts and to solve the said problems. This kind of motorized screw bolt driving tool is as illustrated in FIGS. 1 and 2, which includes a housing 1 having received therein a barrel 20, a detent element 21, a power transmission control element 22, a brake element 23, a driving element 24, a cap 25, a centrifugal element 26, flange 27, and lock pins 281 and 282. The centrifugal element 27 comprises two U-shaped fins 261 and 262 at both lateral sides. During rotation of the centrifugal element 26, the two U-shaped fins 261 and 261 push the flange 27 toward the barrel 20 to further force the front face 221 of the power transmission control element 22 to contact the detent element 21 so that the driving element 24 can be carried to rotate by a motor for further screw bolt driving operation. This type of motorized screw bolt driving tool is expensive to manufacture and inconvenient to assemble. During operation, the engagement of the detent element and the driving element 24 can not be accurately attained.